In many prior situations, multiple sheets of paper have been mechanically fastened together by use of a metal staple or a plastic staple, or by a paper clip, or perhaps by gluing the sheets together. This required an additional operation after the document left a printer apparatus. In addition, the mechanical fastening devices made recycling of the sheet media difficult, due to the presence of these mechanical fastening devices.
In the past, many confidential mailings contained documents such as tax forms, bank statements, insurance statements, medical information, etc. They were typically handled by printing the statement and folding it so that the confidential information becomes located on the interior folded surfaces, and then the statement would be stuffed into an envelope; in that manner the printed information would not be easily seen through the envelope. A second handling method was to print this type of confidential information on forms that were pre-sealed on the edges so that, once delivered to the customer, the form was opened by tearing one or more edges along a perforated line. The forms would then be peeled apart to expose the confidential information. Many types of pre-sealed forms used pressure sensitive paper on one side to record the confidential information between the two sheets of paper. This typically would require a dot matrix printer, or some other type of mechanical impact printing method.
In U.S. Pat. No. 5,213,560, a method for manufacturing sealed envelopes is disclosed, mainly to describe one-piece mailers that can be folded upon themselves and sealed by use of toner strips. The sheet can be provided with printed text, along with the strips of toner of various printing patterns. The toner strips are subsequently heated and the sheet is folded so that the toner strips overlap a folded section of the sheet. Toner is sealed using heat and pressure to create a completed, sealed envelope or package. In one example, a paper web is directed through a printing device, then through a preheat device to soften the strips of toner along the side edges of the paper web. The paper web is then cut into individual sheets, such as letter-sized sheets of paper. After this cut is made, the sheet is folded upon itself, such that the side toner strips come into contact with one another because the side toner strips on the top half of the folded sheet are placed against those on the bottom half of the same folded sheet. This folded sheet is then run through another heating station, at which time the face-to-face toner strips are heated and become bonded to one another, thereby securing the folded paper in a configuration that is sealed along those edges. The opposing (face-to-face) toner strips are placed on each paper surface, and provide a secure bond when they are heated or melted together. This patent discusses the possibility of applying toner to only one side of the paper, however the bond achieved with only a one-sided toner strip is considered generally weaker than two opposing toner strips. On the other hand, a one-sided toner strip can hold the two pieces of paper together until they are to be opened later, at which time the one-sided strip can be removably detached from the other “plain” paper side of the folded mailer. This patent discusses an alternative mode where a printer capable of printing on both sides of a sheet could be used to establish a toner-to-toner joint. This patent also can vary the strip pattern so that it is not necessarily a solid bar of toner. If the strip pattern is varied, the toner density will also be varied, and thus the adhesive strength will be varied. Another alternative is to use opposing cross-hatchings that have sets of lines with unprinted parts of overlapping surfaces. This will result in a somewhat firm, but detachable joint. In yet another embodiment, a relatively solid bar of toner is placed into contact with a group of spaced-apart dots. The density of the dots will then control the adhesive strength of this bond. Another embodiment uses diagonal slashes of toner that are placed into overlapping contact with one another when the sheet is folded and heated. Still another embodiment uses dots of toner around an address window that is to be part of the mailer sheet media. This prevents a person from looking inside the envelope around the clear address window.
U.S. Pat. No. 4,398,986 discloses a binding method that uses re-fusable xerographic toner along an edge of multiple copy sheets, which can be then bound into booklets by arranging the sheets in a stack and re-fusing the toner so that the re-fused toner adheres the adjacent sheets together. This re-fusing operation can be performed after a group of a few sheets is received from a copier, so that the finishing operation can be carried on at the same rate as the copies that are produced by the copier. Alternatively, a larger stack of sheets can be bound together in an off-line operation by a simple heating step. In this patent, a series of rows of alternating rectangular toner strips are placed along the left-hand edge of each of these sheets. A heating shoe is used to press down against the sheets that are to be bonded together with other sheets in the stack. The heating shoe has a movable heating bar that has an elongated surface with a pattern of raised portions and recessed portions. The raised portions have the appearance of small rectangles or ovals. Heat is transmitted from the raised portions to the toner strips of the elongated continuous toner strips on the paper. The recessed portions are located below the level of the raised portions, and will not make contact with the paper that is being bonded to adjacent papers in the stack. The heating shoe is brought against the sheets in the stack with pressure, so that both pressure and temperature are used to bond the toner to the adjacent sheets in the stack. This binding operation can be used for single-sided copies, or for duplex (two-sided) copies that have information copied on both faces of the sheet.
U.S. Pat. No. 5,582,570 discloses a method for binding sheets together using a reactivatable printing substance such as toner along a binding edge of a sheet. Printed text can be simultaneously applied to the sheet by the printing device. Two separate strips of toner placement are available along the edge of the sheet, and as each first sheet is overlaid by a second sheet, the toner strip on the preceding sheet is fused to the uppermost sheet by a strip of toner that is facing downward, thereby binding the sheets together when they are heated. Then the topmost sheet can be printed again (on its other side) with a strip of toner at a different location, with respect to the edge of the sheets that are being bound together. A third sheet can be printed with toner, and then the third sheet is placed so that its toner strip is facing downward, adjacent to the toner strip on the second sheet that is now facing upward. This combination of sheets is then fused together. This can continue for many sheets. A movable heated platen can be rolled along either one of the strip placements, such that the platen presses down against the uppermost sheet at a location where toner is facing downward, but not upward, on that sheet. Then if another sheet is placed thereupon, the movable rolling platen will be rolled along an adjacent strip location to press down against the topmost sheet at placements having toner facing downward, but not upward. In this manner, the platen never touches an upward-facing toner strip. This patent also describes an alternative method of attaching sheets together using alternating rectangles of toner along the same strip. In this alternative embodiment, there are several adjacent rectangles of placement areas that can position toner on the sheet, in which the “even page” placements for these toner rectangles are at different locations than the “odd page” toner placements. When two sheets are to be sealed together, they would use only one set of these toner patch placements, and a platen having one or more rectangular surfaces would press down on the uppermost sheet at locations where the toner is facing only downward. If another sheet is to be overlaid on top of the uppermost sheet at this time, then the odd page rectangles of toner can be used, and the platen can be moved so that it touches the uppermost sheet at only the odd page locations, where toner is not facing upward on that uppermost sheet. The main object of this invention is to allow any sized stack of sheets to be fused together, in a manner that does not require multiple layers to be fused at one time, which can cause uneven heating for different layers of the toner strips. Instead, this patent allows only the uppermost two sheets to be fused at one time, thereby guaranteeing that these uppermost two sheets will receive sufficient heat energy to create a strong bond of toner between the sheets. The lower sheets in the stack were already fused together before each new fusing operation.
Some of the earlier patents that disclose use of toner to bind sheets together are somewhat limited, in that they require a special size or shaped platen to be used, and moreover, the platen must be movable, either in its X-Y positioning on the sheet as it is pressed down against the sheet, or such that it actually moves (rolls) along the surface of the sheet. Others of the earlier patents use a continuous web of paper, rather than individual sheets, and a paper cutting step must be performed. In addition, the cut paper sheet must then be folded so that the toner from one side of the sheet comes into contact with toner (or paper) from the other side of the sheet; thus a folding operation must be performed to complete the sealed package.
Accordingly, it would be an improvement to provide a method and apparatus that can bind two or more sheets together using toner inside a printer, solely by having the two sheets simultaneously pass through the fuser of a standard EP printer or laser printer, without the need for a folding step and without the need for a movable platen for applying heat and pressure, and with complete freedom as to the exact placement of the toner strips that are to bind the sheets together.